Recreational activities, classes and tours have been relocated from a Torrance preserve after the marsh was temporarily closed amid heightening concerns over the West Nile Virus and the first confirmed death this year in Southern California due to the disease.

City officials said the closure, effective immediately, was “a precautionary measure,” based on data from the local vector control office, and that the marsh will remain closed indefinitely.

In the meantime, regularly scheduled classes and tours are being moved from the marsh to a nature center across the street.

“Nothing is altered. We’re holding all of the classes as scheduled,” said Tracy Drake, manager of the nature center.

Local vector control officials said that two weeks ago, one of the marsh’s sentinel chickens contracted West Nile. Last week, five more tested positive, and active mosquito pools carrying the disease were found nearby.

“You put mosquitoes and positive birds and water together, and you always run a risk,” said Robert Saviskas, executive director of the Los Angeles County West Vector Control department.

He added that the agency plans to conduct door-to-door surveys in Redondo Beach and Torrance over the next week to raise awareness, including in areas around the preserve, which is located near a number of apartment buildings and a gated community.

The closure of Madrona Marsh, a 10-acre wetlands area popular with bird-watchers, comes on the heels of the first reported West Nile death in Southern California this year.

The Los Angeles County Department of Public Health confirmed the death of a South Bay man due to the virus last week. The number of confirmed human cases of West Nile Virus in L.A. county jumped from 5 to 13 last week, according to the department’s report.

More than half of confirmed West Nile virus diagnoses this year have been in the South Bay.

County public health officials say it’s still very early in the season, but that the total number of confirmed cases is up from this time last year, which was a very active year for West Nile virus.

“I would not yet get out the red flag,” said Dr. Laurene Mascola, who is chief of the county’s acute communicable disease control unit.

Still, South Bay vector control officials are watching the region’s activity closely. “The South Bay is unusual this year because normally, when it’s near the coast and there’s cooler temperatures, the activity of the mosquitoes is much lower,” Saviskas said.

“We may be seeing the beginning of a very active year.”

City officials also plan to drain a pool that’s usually used to pump water into the preserve, Saviskas said.

“The health and safety of our citizens is our highest priority,” the city said in a statement. “We will continue to be diligent as we monitor the situation carefully and will notify the public as soon as possible about the re-opening of the preserve.”

The city further advised residents to limit their activity during dusk and dawn in the area, which is near the Del Amo Fashion Center mall, and to wear insect repellent containing DEET, long-sleeved shirts and pants.